All cpus in your system must have support for Intel64 or Amd64 with hardware virtualization option enabled and NX flag on. Take also into account that a large amount of ram is required although the KVM overcome the problem of low physical amounts.
Once you implement a device passthrough or device assignment be advised that the cpu must use IOMMU like IBM POWER8 architecture, firmware also uses IOMMU, cpu roots parts and PCIe devices must have ACS capabilities.
